package org.foreningsgatan.modular.common.primitive;

/*
 * Copyright (c) 2008 Joakim Back
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 * 
 */

/**
 * Interpolation
 * 
 * Provides methods for retrieving interpolated values between indices in
 * arrays of doubles. That is, a kind of floating point indices.
 * 
 * Implemented using formulas defined at
 * http://freespace.virgin.net/hugo.elias/models/m_perlin.htm
 * 
 * @author Joakim Back
 * 
 */
public class Interpolation {
	public static double getLinear(double[] pValues, double vIndex) {
		int ia = PrimitiveUtils.wrap(0, pValues.length - 1, (int) Math
				.floor(vIndex));
		int ib = PrimitiveUtils.wrap(0, pValues.length - 1, (int) Math
				.ceil(vIndex));

		double a = pValues[ia];
		double b = pValues[ib];

		double x = vIndex % 1;

		return a * (1 - x) + b * x;
	}

	public static double getCosine(double[] pValues, double vIndex) {
		int ia = PrimitiveUtils.wrap(0, pValues.length - 1, (int) Math
				.floor(vIndex));
		int ib = PrimitiveUtils.wrap(0, pValues.length - 1, (int) Math
				.ceil(vIndex));

		double a = pValues[ia];
		double b = pValues[ib];

		double x = vIndex % 1;
		double ft = x * Math.PI;
		double f = (1 - Math.cos(ft)) * 0.5;

		return a * (1 - f) + b * f;
	}
}
